PlaneRacer- I agree its definetely not 90% RTF out of box... I found the instructions adequate and had no problems with assembly as all parts fit well.
As to painting etc. I glassed the wings and tail on my Bipe. First lightly sand plastic parts eg. fuz and inner cabane struts and prime. I used Top Flite Lustrekote primer and colour coats... Then used the stock firewall and preped inside the forward section of fuz where firewall sits by sanding plastic with 80 grit sandpaper. Although at the time I glued firewall with 30 epoxy, if I was to do it again I would use either BVM Aeropoxy or Loctite Hysol epoxy glues as these are much stronger. After glueing firewall in place I ran four small self taping machine screws through front of fuz to pin the firewall, this has worked well and has never looked like being a concern....
As to engine size- I have flown my Bipe with an O.S. 91 and Y.S. 91 four stroke with 16x6 and 16x8 props and it performes great.... The one major modification I would recommend is to do away with the single centre mounted aileron set up and install 2 x servos, one each outbord in each wing for the ailerons, reason for this is I have had mild aileron flutter at high speed with the standard kit designed central aileron design. Mind you the model is only designed for 40-60 2 stroke engines, and I have been flying mine mostly with a Y.S.91 By the way I have about 300 flights on my bipe over 6 years and still going strong. You will love this models flying qualitys, its every bit as aerobatic as a Pitts Special yet has the unique EAA AcroSport semi scale look

Let me know if you have any further questions [8D]